The Nurses' Health Study (NHS), as well as the NHSII (used in Project 3), are prospective cohort studies of about 238,000 women. A unique aspect of the studies are the collection of biologic specimens that can be used to further elucidate molecular mechanisms of disease through examination of genetic and epigenetic variation, circulating biomarkers, and tumor tissue markers. We have collected blood samples on over 60,000 women, urine for nearly 50,000 women, cheek cell DNA for over 60,000 women without blood samples, and thousands of tumor tissue blocks. These samples are a valuable but finite resource, thus we put substantial effort into ensuring high quality and efficient specimen handling and piloting new assay methodology in a cost-effective, ethical, state of the art manner. The aim of the Biologic Specimen Management Core (Core C) is to collect, store, process, and distribute biological specimens from women in the NHS/NHSII to better understand the etiology of cancer. Specifically, we aim to provide biologic specimens, including plasma, urine, buffy coat, red blood cells, and cheek cell DNA, for nested case-control studies of breast, colorectal, and ovarian cancers through the NHS Biomarker Laboratory and Repository. Further we will provide tumor tissue for studies of breast, colorectal, and ovarian cancer, as well as mammographic density measures for breast cancer, and to collect and process related specimens via the NHS Tissue and Mammogram Repository. To support these repositories we will maintain and improve an over-arching project management and sample tracking laboratory information management system (LIMS). Central activities of this core include collection of new specimens, processing of samples, management and maintenance of related biorepositories, and preparation of specimens for assay. Importantly, the core conducts pilot studies of all new assays to ensure high reproducibility before sending participant specimens for analysis; quality control procedures also allow for real-time tracking of assay quality while participant samples are being analyzed. Notably, this Core supports scientific aims in Projects 1 -4 of the current application.